How do fishes survive in frozen lakes? - Physics

Short Note

How do fishes survive in frozen lakes?



Fishes survive in pond even when the atmospheric temperature is below 0°C. It is because of anomalous expansion of water. When the temperature falls below 0°C water changes into ice and rises to the top and ice being poor conductor of heat helps to keep water below it at 4°C and fish can live in pond water.

Concept: Anomalous Expansion of Water
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Chapter 6: Heat and Energy - Exercise



Water is used as a cooling agent.

Give reason of Water pipes burst in severe winter.

Give reason of Ice floats on water.

 Give reason for Sea water does not freeze at 0°C.

How does the anomalous expansion of water help aquatic organisms in cold climates?

Fill in the blank and rewrite the sentence.

The amount of water vapour in air is determined in terms of its ........... .

Observe the following graph. Considering the change in volume of water as its temperature is raised from 0°C, discuss the difference in the behaviour of water and other substances. What is this behaviour of water called?

Explain the following:

What is the role of the anomalous behaviour of water in preserving aquatic life in regions of cold climate?

Answer the following:

On what basis and how will you determine whether air is saturated with vapour or not?

1 kg of ice at 0°C is mixed with 1 kg of steam at 100°C. What will be the composition of the system when thermal equilibrium is reached? Latent heat of fusion of ice = 3.36 × 103 J kg−1 and latent heat of vaporization of water = 2.26 × 106 J kg−1.

Calculate the time required to heat 20 kg of water from 10°C to 35°C using an immersion heater rated 1000 W. Assume that 80% of the power input is used to heat the water. Specific heat capacity of water = 42000 J kg−1 K−1.

On a winter day the temperature of the tap water is 20°C whereas the room temperature is 5°C. Water is stored in a tank of capacity 0.5 m3 for household use. If it were possible to use the heat liberated by the water to lift a 10 kg mass vertically, how high can it be lifted as the water comes to the room temperature? Take g = 10 m s−2.

A 50 kg man is running at a speed of 18 km h−1. If all the kinetic energy of the man can be used to increase the temperature of water from 20°C to 30°C, how much water can be heated with this energy?

Consider the situation of the previous problem. Assume that the temperature of the water at the bottom of the lake remains constant at 4°C as the ice forms on the surface (the heat required to maintain the temperature of the bottom layer may come from the bed of the lake). The depth of the lake is 1.0 m. Show that the thickness of the ice formed attains a steady state maximum value. Find this value. The thermal conductivity of water = 0.50 W m−1°C−1. Take other relevant data from the previous problem.

A calorimeter contains 50 g of water at 50°C. The temperature falls to 45°C in 10 minutes. When the calorimeter contains 100 g of water at 50°C, it takes 18 minutes for the temperature to become 45°C. Find the water equivalent of the calorimeter.

Explain the following

A glass bottle completely filled with water and tightly closed at room temperature is likely to burst when kept in the freezer of a refrigerator. 

Water is cooled from 4 °C to 0 °C. It will :

Density of water is maximum at :

Explain, why are soft drink bottles not completely filled?

In cold countries, the water pipes are covered with poor conductors. Why?

Water at 0°C is heated to 10°C. Sketch a temperature-volume graph to show the behavior of heating.

Study the following diagrams and write down your observations.

How will you demonstrate thermal expansion in liquids? Describe an experiment.

At what temperature the density of water is maximum?

What is the usual range of temperature marked on a clinical thermometer?

Observe the given graph and answer the following questions:

  1. Name the process represented in the figure.
  2. At what temperature does this process take place?

_______ apparatus is used to study the anomalous behaviour of water.

Write the name.

The instrument used to study anomalous behaviour of water.

Write scientific reason.

Fish can survive even in frozen ponds in cold regions.

Write scientific reason.

Placing a plastic bottle filled with water in the freezing compartment in the freezer can cause the bottle to explode.

Draw a neat and labelled diagram of Hope’s apparatus.

Name the following diagram appropriately.

Write a short note.

Anomalous behaviour of water

Observe the given picture and answer the following questions.

  1. Which property do you understand in this picture?
  2. What is the temperature of the water at the surface?
  3. What is the temperature below the layer of ice on the surface?

Match the columns:

Column ‘A’ Column ‘B’
The density of water is maximum at (a) 0°C
  (b) 4°C
  (c) 100°C

A graph between the volume and temperature of water is shown. Explain the anomalous behaviour of water.


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